Method of and apparatus for defrosting absorption

ABSTRACT

In absorption refrigeration apparatus in which circulation of inert gas is effected through and between an evaporator and absorber of an inert gas circuit by a force developed by the difference in specific weight of columns of gaseous fluid, defrosting of the evaporator is effected by blocking the circulation of inert gas in its circuit. This is accomplished by providing structure including a U-shaped trap which is associated with the inert gas circuit and in which liquid in the apparatus collects. The structure embodies a siphon which renders it inoperable to block the circulation of inert gas in its circuit responsive to accumulation of liquid above a first level in the trap and subsequently renders it operable to block the circulation of inert gas responsive to accumulation of liquid above a second level in the trap. When the liquid has accumulated to a third level in the trap the siphon functions to remove the liquid therefrom and render the structure inoperable to block the circulation of inert gas in its circuit.

United States Patent [191 Eber et a].

l l 1451 Apr. 30, 1974 METHOD OF AND APPARATUS FOR Primary Examiner-William F. ODea DEFROSTING ABSORPTION Assistant Examiner-Peter D. Ferguson [75] Inventors: Nicolas Eber, Zurich; Amram Asher, Attorney Agent or Firm-Edmund Fenander 'Oberengstringen, both of Switzerland I [73] AS-Signee: salilab'iskgengesenschafi Zurich In absorption refrigeration. apparatus in which circula- Sw'tzer an tion of inert gas is effected through and between an [22] Filed: Aug. 23, 1972 evaporator and absorber of an inert gas circuit by a force developed by the difference in specific weight of [21] Appl' 283191 columns of gaseous fluid, defrosting of the evaporator is effected by blocking the circulation of inert gas in [30] Foreign Application Priority Data its circuit. This is accomplished by providing structure Sept. 3 1971 Sweden 11229/71 including a U'shaPed trap which is associated with the inert gas circuit and in which liquid in the apparatus 52 us. c1. 62/110, 62/490 collect? [51] Int. Cl. F25b 15/10 The structure embodies a siphon which renders it [58] Field of Search 62/490, 476, 277, 110 inoperable to block the'circulation of inert gas in its circuit responsive to accumulation of liquid above a [56] References Cited first level in the trap-and subsequently renders it UNITED STATES PATENTS operable to block the circulation of inert gas I 993 129 N19 Baird 62,110 ,X responsive to accumulation of liquid above a second 2:269:102 H1942 h 62 10 X level in the trap. When the liquid has accumulated to 2 4 8 104 4/1949 ph m 2] 10 x a third level in the trap the siphon functions to remove 3,063,257 11/ 1962 Phillips 62/490 X the liquid therefrom and render the structure 3,177,675 4/1965 Kogel 62/490 X inoperable to block the circulation of inert gas in its 3,580,004 5/1971 Kogel 62/490 x circuit. 1 3,678,699 7/l972 Holleitner 62/490 X 16 Claims, 4 Drawing Figures 2% FREEZER 60 23 zz'zzzzzzmzzzzazzz my TMPE/Pflfl/ 26 35 34 em azflme. 'FOOD era/e465 64 sear/01v 65 66 5 405 E V l I/ m 5 j 40 5 6 xl/sx/ Ill/EA ME 274/044, 35 30 306L 301,

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METHOD OF AND APPARATUS FOR DEFROSTING ABSORPTION BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to defrosting of evaporator structure or cooling units of absorption refrigeration apparatus of the inert gas type.

2. Description of the Prior Art It has been proposed heretofore to melt frost formed on cooling units of absorption refrigeration apparatus of the inert gas type by flowing a hot working fluid, such as refrigerant vapor, to the cooling units. When hot refrigerant vapor is employed for defrosting a liquid trap is usually provided which blocks off the path of flow of the hot vapor to the cooling unit, the liquid being removed from the trap to start defrosting. When this occurs hot refrigerant vapor flows directly to the cooling unit and is diverted from its normalpath of flow to the condenser in which it is liquefied and flows to the cooling unit to produce useful refrigeration.

Absorption refrigeration apparatus of the inert gas type are often provided in which the liquid trap referred to above is absent. In such apparatus it then becomes necessary to provide such a liquid trap to flow hot refrigerant in a path of flow which by-passes the condenser. This often'impairs the desirable operating characteristics of the generator or boiler unit which is objectionable.

SUMMARY OF THE INVENTION It is an object of our invention to provide an improvement for defrosting the evaporator or cooling unit of absorption refrigeration apparatus of the inert gas type by blocking and reducing the circulation of inert gas therein. We accomplish this by providing structure including a trap having a pair of upstanding legs, one of which is connected in the inert gas circuit and the other of which is connected to receive vapor from the boiler or generator unit and condenser therein. The structure embodies a siphon which renders it inoperable to block the circulation of inert gas in its circuit responsive to accumulation of condensate above a first level in the trap and subsequently renders it operable to block the circulation of inert gas responsive to accumulation of condensate above a second level in the trap. When the condensate has accumulated to a third level in the trap the siphon functions to remove the liquid therefrom and render the structure inoperable to block the circulation of inert gas in its circuit.

BRIEF DESCRIPTION OF THE DRAWING Referring to FIG. 1, we'have shown our invention in connection with a hermetically sealed absorption refrigeration system of a uniform pressure type in which an auxiliary pressure equalizing gas is employed. Aircooled systems of this type are well known and include a cooling unit or evaporator structure E which is arranged to abstract heat from the thermally insulated interior of a refrigerator cabinet 60. Refrigerant fluid,

such as ammonia, passes through a conduit 26 into the evaporator structure E and evaporates and diffuses therein into an inert gas, such as hydrogen, to produce a refrigerating effect. The resulting gas mixture of refrigerant and inert gas flows from evaporator structure E through an outer passageway 30a of a gas heat exchanger 30 and vertically extending conduit 31 into an air-cooled absorber comprising an absorber vessel 21 and a looped absorber coil 20.

In the absorber refrigerant vapor is absorbed by a suitable absorbent, such as water, for example, which is introduced into coil 20 through a conduit 19. The hydrogen or inert gas, which is practically insoluble and weak in refrigerant, is returned to evaporator structure E in'a path of flow which includes conduit 32, the lefthand leg 37 of a U-shaped trap 36 and an elongated tube 33. The elongated tube 33 forms the inner passageway 30b of the gas heat exchanger 30 and extends lengthwise within the evaporator structure E and inert gas weak in refrigerant passes from the upper open end thereof into the presence of refrigerantfluid for downward flow through the evaporator structure .E.

The circulation of gas in the inert gas circuit just described is due to the difference in specific height of the columns of gas rich and weak, respectively, in refrigerant vapor. Since the column-of gas rich in refrigerant vapor and flowing from the evaporator structure E to the absorber coil 20 is heavier than the gas weak in refrigerant vapor and flowing from such coil to the evaporator structure E, a force is produced or developed ing tube 12 is heat conductively connected at 13 and 14, respectively, to the pipe 15 and pump 16. By heating the generator G, as by an'electrical heating element 11 disposed within the heating tube 12, liquid from the pump 16 is raised by vapor lift action through the riser tube 17 into the upper part of the boiler pipe 15. The liberated lifting vapor entering the boiler pipe 15 through the riser tube 17, and also vapor expelled from solution in the boiler pipe, flows upward through a conduit or vapor line 23 to acondenser 25 having cooling fins 24.

Refrigerant vapor is liquefied in the condenser 25 by surrounding cooling air which flows over the fins 24 and liquefied refrigerant is returned to the evaporator structure through the conduit 26 to complete the refrigerating cycle. Liquid refrigerant flows by gravity in the evaporator structure E, the refrigerant flowing in parallel flow with the inert gas in a low temperature section 28 and then in a higher'temperature section 29 changer 62. Circulation of abosrption solution in the manner just described is due to raising of liquid to a high level in boiler pipe from which liquid can flow by gravity to the upper end of the absorber coil 20.

The parts of the generator or boiler G are enveloped by a body of insulation 63 retained in a shell or casing 64. The outlet end of the condenser 25 is connected by a conduit'35 to the gas circuit, as at the conduit 31, for example, so that any non-condensable gas which may pass into the condenser can flow to the gas circuit and not be trapped in the condenser.

The refrigerator system can be controlled by a thermal bulb 65 which is affectedby a temperature condition of evaporator section 29. The thermal bulb 65 is connected by a conduit 66 to a control device 67 which is connected in one of the conductors 10 for supplying electrical energy to the heating element 11. The thermal bulb 65 and conduit 66 form part of an expansible fluid thermostat which is charged with a suitable vola-- tile fluid and responds to changes in a temperature condition affected by high temperature evaporator section 29 to operate control device 67 and connect and disconnect the heating element 11 to and from the source of electrical supply.

The refrigerating effect produced by the upper evaporator section 28, which 'is adapted to be operated 'at temperatures substantially below freezing, is primarily utilized to effect cooling of an upper freezer space which is defined by a partition 68 and the thermally insulated walls of the cabinet 60. The refrigerating effect produced by the lower evaporator section 29, which is adapted to be operated at a higher temperature than that of evaporator section 28, and also desirably below freezing, is primarily utilized to cool air in an unfrozen food storage space below the partition 68. It will be seen that the conduit 26 for conducting liquid refrigerant from condenser 26 to the evaporator structure E is heat conductively connected to both the evaporator sections 28 and 29. In this way liquid refrigerant is effectively pre-cooled before flowing into the presence of inert gas at the extreme upper end of the evaporator structure E. To increase the effective heat transfer surface of the lower evaporator section 29 so as to promotecooling of air in the food storage space, a plurality of fins or heat transfer members 69 may be secured thereto in any suitable manner.

Although the refrigerator cabinet 60 is only diagrammatically illustrated, it will be understood that the top freezer space is provided with a separate closure member (not shown) from that provided for the unfrozen food storage space. While frost accumulates on both the evaporator sections 28 and 29, suchaccumulation of frost takes place much more slowly in the freezer space than in the unfrozen food storage space because the need for gaining access into the former is considerably less than that for the latter. When a layer of frost of considerable thickness is allowed to accumulate on the lower evaporator section 29, the efficiency of the refrigeration apparatus is reduced considerably and the apparatus operates for longer periods of time to maintain the unfrozen food storage space at a desired low temperature than otherwise would be necessary.

In order to effect defrosting of the evaporator section 29 the normalcirculation of inert gas through and between the evaporator structure E and absorber coil 20 is interrupted and reduced. In accordance with our invention we accomplish this by providing the U-shaped trap 36 having a pair of upstanding legs 37 and 38, the left-hand leg 37 of which forms a part of the inert gas circuit, as explained above. Thus, inert gas weak in refrigerant flows from the upper end of the absorber coil 20 through conduit 32 into the left-hand leg 37 of trap 36 which is connected thereto. Inert gas weak in refrigerant flows from the U-shaped trap 36 to the upper end of the evaporator section 28 through the elongated tube 33, the lower end 41 of which is disposed in the left-hand leg' 37 of the trap.

The right-hand leg 38 of the U-shaped trap 36 is arranged to receive from the generator or boiler G vapor expelled from absorption solution therein. As shown, this is accomplished by flowing expelled vapor from the upper part 39 of boiler pipe 15 to the right-hand leg 38 of trap 36 in a path of flow which includes conduits 40 and 42. Y

The vapor expelled from solution in'the generator or boiler G and flowing therefrom includes refrigerant vapor and accompanying water vapor. An air-cooled rectifier (not shown), which is well known, can be provided in the vapor line 23. The water vapor is condensed in the rectifier and drains back to the boiler pipe 15. However, some expelled refrigerant vapor and accompanying water vapor is diverted from the vapor line 23 into the conduits 40 and 42. Such diverted vapor diffuses slowly into the U-shaped trap 36 and continuously condensestherein.

When the quantity of liquid accumulated in the U- shaped trap 36 is above a first level to close and seal the lower end of the trap, normal operation of the refriger-' ation apparatus is effected and the evaporator structure E produces useful refrigeration. Under such normal operating conditions inert gas weak in refrigerant flows from the upper end of the absorber coil 20 through conduit 32, the left-hand leg 37 of the trap 36 and tube 33 to the upper end of the evaporator section- 28.

During normal operation of the refrigeration apparatus and after the liquid accumulated in the trap 36 closes and seals the lower end thereof, liquid condensate continues to collect in the trap until it reaches the lower open end 41 of the elongated tube 33. When this occurs the circulation of inert gas in its circuit is throttled and blocked. This materially reduces the normal circulation of inert gas and rapid defrosting of the evaporator section 29 is'promoted because, under these conditions, the evaporator structure E cannot produce useful refrigeration, Hence, it can be stated that when the quantity of liquid accumulated in the trap 36 is such that the liquid rises above a second level, the normal circulation of inert gas in-its circuit is blocked and defrosting is initiated automatically.

When this operating condition occurs vapor continues to be expelled from solution in the generator G. And, since the refrigeration apparatus is of the kind in which no liquid trap is provided in the vapor line 23 leading to the condenser 25, expelled vapor continues to flow to the condenser and condenses therein. The same will be true in refrigeration apparatus of the kind having an analyzer in the vapor line leading to the condenser. The condensate formed in the condenser 25 under these conditions is at an elevated temperature. And, since the evaporator structure E is not producing useful refrigeration, the relatively hot condensate introduced into the evaporator structure E effects heating of the evaporator section 29. to melt frost on such section and the heat transfer members 69 fixed thereto.v

The liquid level in the trap 36 continues to rise during defrosting. And the rate at which this liquid level rises can be adjusted by the dimensions selected for the conduit 42 which extends upward from the right-hand leg 38' of the trap 36 and forms a part thereof. The conduit 42 extends upward a short distance from a vertical position which is more or less the same as the vertical position of the lower end 41 of the elongated tube 33. In the preferred embodiment being described the conduit 42 has a cross-sectional area which is considerably smaller than that of the remaining part of the righthand leg 38 of the trap 36. When the quantity of liquid accumulated in the trap 36 is such that the level of the liquid is at the lower end 41 of the elongated tube 33, the liquid level will rise much faster than before with continued accumulation of liquid in the trap.

A siphon 43 is connected to the left-hand leg 37 of the trap 36. The highest point 44 of the siphon is [0- I cated at a suitable level above the lower end 41 of the elongated tube 33. When the quantity of liquid accumulated in the trap 36 is such that the liquid level therein is at the same height as the highest point 44 of the siphon, which may be referred to as the overflow point, liquid is siphoned from the trap 36 through the left-hand arm of the siphon into the absorber vessel 21, thereby enabling inert gas weak in refrigerant to return from absorber coil to the evaporator structure E.

The liquid collected in the trap 36 essentially constitutes absorption liquid or solution which is rich in refrigerant. Such liquid siphoned from the trap 36 into absorber vessel 21 flows therefrom through conduit 22 a to the pump 16 which operates at its normal operating temperature when defrosting is being effected. During defrosting periods liquid condensate formed in the condenser 25 and introduced into the evaporator structure E through the conduit 26 does not evaporate in the evaporator structure but simply flows through the evaporator sections 28 and 29, outer passage 30a of the gas heat exchanger 30 and conduit 31 into the absorber vessel 21. It is necessary to connect the right-hand arm of the siphon 43 to the lefthand leg 37 ofthe trap 36 at such a height that the trap will not be depleted of liquid when liquid is siphoned therefrom. In other words, the quantity of liquid remaining in the trap after the siphoning action is completed must be sufficient to seal and close the lower end of the trap so that vapor from the upper part 39 of the boiler pipe 15 cannot pass through the trap into parts through which absorption liquid normally circulates.

As explained above, the interval of time during which defrosting takes place can be increased or decreased by changing the relative vertical positions of the lower end 41 of the elongated tube 33 and the overflow point 44 of the siphon 43 and by increasing or decreasing the cross-sectional area of the conduit 42. Further, by changing the shape of the trap 36 and parts connected thereto, it is also possible to increase or decrease the interval of time between two successive defrosting periods.

FIG. 2 illustrates another embodiment of our invention in which parts similar to those shown in FIG. 1 are referred to by the same reference numerals. The embodiment of FIG. 2 differs from FIG. 1 in that inert gas weak in refrigerant flows directly from the looped coil 20 to the upper end of the evaporator section 28 through a conduit 51 and elongated tube 33. Inert gas rich in refrigerant flowsfrom the outer passage 30a of the gas heat exchanger 30 to the absorber vessel 21 through a conduit 50 having a U-shaped trap 52.

During normal operation of the refrigeration apparatus unevaporated refrigerant flows by gravity from the evaporator section 29 through the outer passage 30a of the gas heat exchanger 30 and conduit 50 and accumulates in the trap 52. When a sufficient quantity of liquid collects in the trap 52 and its surface is above a first level the liquid closes and seals the trap and blocks the circulation of inert gas in its circuit.

A siphon is provided for the trap 52, its short leg 53 being connected to the bottom of the trap and its long leg 55 being connected to the absorber vessel 21. When the quantity of liquid accumulated in the trap is such that liquid in the short leg 53 of the siphon reaches the overflow point 54, liquid in the trap is siphoned to the absorber vessel 21. By providing a siphon having a suitable height and a U-shaped trap 52 of suitable dimensions, both the length of the defrosting periods and the interval of time between successive defrosting periods can be determined. A

During normal operation of the refrigeration apparatusthe liquidaccumulating in the U-shaped trap 52 comprises unevaporated refrigerant passing from the evaporator structure, as explained above, and absorption liquid which has condensed in the outer passage 30a of the gas heat exchanger. The quantity of liquid accumulating in the U-shaped trap 52 increases slowly during normal operation of the refrigeration apparatus when the inert gas circulates in its circuit at a normal rate and is not blocked or interrupted. But when the normal circulation of inert gas is interrupted and blocked, theentire quantity of condensed refrigerant formed in the condenser 25 and introduced into the evaporator structure E flows therethrough and the gas heat exchanger 30 and conduit 50 into the U-shaped trap 52'. When this occurs the liquid level in the U- shaped trap 52 rises rapidly. 7

An advantage of the embodiment of FIG. 2 is that, when defrosting is being effected, absorption liquid or solution rich in refrigerant flows from the absorber vessel 21 to the pump 16, thereby maintaining the latter and the riser tube 17 at its intended operating'tempera-' ture.

In the first-described embodiment of FIG. 1 liquid accumulated in the U-shaped trap 36 comprises condensate which flows downward in the right-hand leg 38 of the trap and also condensate which is formed inthe elongated tube 33 and flows downward in the left-hand leg 37 thereof. Since the rate at which condensate is formed in the elongated tube 33 increases and decreases with changes in the temperature of ambient air, this can adversely affect the manner in which defrosting takes place. Most important, the defrosting periods will not occur at'regular intervals of time. In order to overcome this disadvantage which is present in the embodiment of FIG. 1, we have provided another embodiment of our invention which is illustrated in FIG. 3 and in which parts similar to those shown in FIG. 1 are referred to by the samereference numerals.

In FIG. 3 condensate formed in the elongated tube 33 of the gas heat exchanger 30, through which inert gas weak in refrigerant returns to the evaporator section 28 from the absorber coil 20, is prevented from flowing to the left-hand leg 37 of the U-shaped trap 36. In FIG. 3 the gas heat exchanger 30' extends vertically downward from the evaporator section 29 to the absorber vessel 21. And the elongated tube 33 includes an extension 57 at its lower part which extends downward within the gas heat exchanger 30' into the absorber vessel 21 below the liquid surface level therein.

A conduit or tube 58, which is connected at 58 to the extension 57, includes a horizontally extending part 58a inclined downward to the connecting point 58 and a vertical part 58!) extending downward in the left-hand leg 37 of the U-shaped trap 36. It will be understood that the vertical part 58b of the conduit or tube 58 corresponds to the lower end 41 of the elongated tube 33 in FIG. 1 and that the circulation of inert gas in its circuit will be blocked by liquid inthe same manner in FIG. 3 as in FIG. 1. However, any condensate formed in the elongated tube 33 in FIG. 3 cannot flow to the U-shaped trap 36 but instead will flow downward through the extension 57 into the absorber vessel 21.

A further embodiment of the invention is illustrated in FIG. 4, in which parts similar to those shown in FIG. 3 are referred to by the same reference numerals.

In FIG. 4 the upper end of the absorber through a conduit 70 is connected to the elongated inner tube 33 of the gas heat exchanger 30'. Inert gas weak in refrigerant'passes this way from the absorber 20 to the evaporator section 28.

The inert gas rich in refrigerant vapor coming from the evaporator sections 28 and 29 through the gas heat exchanger 30' is conducted through conduit 71 to the left-hand leg 37 of the U-shaped trap 36. The rich gas flows into the lower end 41 of a conduit 72, the other end o f which is connected to the absorber vessel 21 above the liquid therein so that the gas can flow into the lower end of the absorber 20.

In FIG. 4 the extension 57 of the elongated tube 33 extends into the absorber vessel 21 below the liquid surface level therein. So does also an extension 73 of the outer conduit of the gas heat exchanger 30".

We claim:

1. In a method of refrigeration which includes a. expelling refrigerant from absorption solution at a place of vapor expulsion and flowing solution weak in refrigerant therefrom toa place of absorption,

b. liquefying the expelled refrigerant at a place of condensation and flowing the condensate to a place of evaporation,

c. evaporating the refrigerant in the presence of an inert gas at the place of evaporation to produce a refrigerating effect,

d. circulating the inert gas in a circuit between the place of evaporation and the place of absorption, and

e. flowing solution rich in refrigerant from the place of absorption to the place of vapor expulsion,

f. the place 'of evaporation being subject to formation of frost due to said refrigerating effect,

g. the steps of collecting liquid in a trap above a first level to close and seal the lower end of the trap,

h. continuing to collect liquid in the trap above a second higher level to block-the circulation of inert gas in the circuit to melt any frost formed at the place of evaporation, and

i. continuing to collect liquid in the trap until it reaches a third higher level to remove liquid from the trap and open the seal at the lower end thereof.

2. The method set forth in claim 1 in which the liquid collected in the trap above the second higher level blocks the circulation of inert gas in that part of the circuit in which inert gas rich in refrigerant flows from the place of evaporation to the place of absorption.

3. The method set forth in claim 1 in which the liquid collected in the trap above thesecond higher level blocks the circulation of inert gas in that part of the circuit in which inert gas weak in refrigerant flows from the place of absorption'to the place of evaporation.

4. The method set forth in claim 1 in which the liquid collected in the trap abovethe first level closes and seals the lower end thereof to initiate the production of refrigeration at the place of evaporation.

5. Absorption refrigeration apparatus of the inert gas type comprising a. interconnected parts including b. a gas circuit having a cooling element in which liquid refrigerantevaporates in the presence of inert gas to produce a refrigerating effect,

0. means for blocking circulation of inert gas in its circuit, said means being arranged to'collect liquid above a first level to second and third higher levels,

d. said means being rendered operable to block circulation of inert gas in its circuit responsive to the liquid therein reaching the second level, and

. e. said blocking means embodying provisions for transferring liquid therefrom to another part of the apparatus responsive to the liquid therein reaching the third level.

6. Absorption refrigeration apparatus as set forth in claim 5 in which I a. said means for blocking circulation of inert gas comprises a trap having a pair of upstanding. legs arranged to collect the liquid, and

b. said inert gas circuit including at least one leg of said trap,

c. said trap being rendered operable to block circulation of inert gas in its circuit responsive to the liquid therein reaching the second level.

' 7. Absorption refrigeration'apparatus as set forth in claim 6 in which said provisions embodied in said blocking means for transferring liquid therefrom to another part of the apparatus comprises a siphon."

8. Absorption refrigeration apparatus as set forth in claim 7 in which said gas circuit includes an absorber and a vessel connected to receive liquid from said absorber, the outlet of said siphon being connected to discharge liquid to said vessel.

9. Absorption refrigeration apparatus as set forth in claim 5 in which I a. said gas circuit includes an absorber, first conduit means for flowing inert gas weak in refrigerant from said absorber to said cooling element and second conduit means for flowing inert gas rich in refrigerant from said cooling element to said absorber,

b. said means for blocking circulation of inert gas being constructed and arranged to block the circulation of inert gas in said first conduit means.

10. Absorption refrigeration apparatus as set forth in claim 9 in which a a. said absorber includes an absorber vessel connected to receive liquid from said absorber,

b. said cooling element comprising an elongated hollow member and one section of said first conduit means including piping extending lengthwise within said hollow member,

c. another inclined section of said first conduit means being interposed between said one section thereof and said blocking means, and

d. a conduit depending downward from the juncture of said one and other inclined sections of said first conduit means, said last-mentioned conduit having a lower open end which is below the liquid surface level in said absorber vessel.

11. Absorption refrigeration apparatus as set forth in claim in which a. said gas circuit includes said cooling element and an absorber, first conduit means for flowing inert gas weak in refrigerant from said absorber to said cooling element and second conduit means for flowing inert gas rich in refrigerant from said cooling element to said absorber,

b. a circuit for circulation of absorption liquid including said absorber and a vapor expulsion unit,

c. means including a vapor line and a condenser interconnecting said vapor expulsion unit and said cooling element,

d. said means for blocking circulation of inert gas comprising a trap having a pair of upstanding legs, one of said legs forming a part of said first conduit means of said gas circuit and the other of said legs being connected to receive vapor from said vapor expulsion unit, and

c. said first conduit means of said gas circuit including piping depending downward in said one leg of said trap and having the lower open end thereof below the level to which liquid can rise in said one leg.

l2. Absorption refrigeration apparatus as set forth in claim 11 in which the other of said legs of said trap connected to receive vapor from said vapor expulsion unit, in an upward direction from a region at substantially the same level as the lower open end of said piping, has a cross-sectional area smaller than that of other parts of said trap.

13. Absorption refrigeration apparatus as set forth in claim 5 in which a. said gas circuit includes an absorber, first conduit means for flowing inert gas weak in refrigerant from said absorber to said cooling element and second conduit means for flowing inert gas rich in refrigerant from said cooling element to said absorber,

b. said means for blocking circulation of inert gas being constructed and arranged to block the 'circulation of inert gas in said second conduit means.

14. Absorption refrigeration apparatus as set forth in claim 13 in which a. said absorber includes an absorber vessel connected to receive liquid from said absorber,

b. said second conduit means being connected to said absorber vessel,

c. said means for blocking circulation 'of inert gas comprising a trap in said second conduit means,

and

d. said provisions embodied in said blocking means for transferring liquid therefrom to another part of the apparatus comprising a siphon.

l5. Absorption refrigeration apparatus as set forth in claim 14 in which the discharge end of said siphon is connected to said absorber vessel.

16. Absorption refrigeration apparatus as set forth in claim 5 which includes a. a condenser for liquefying refrigerant vapor and a conduit for conducting liquid refrigerant from said condenser to said cooling element, Y

b. said last-mentioned conduit being heat conductively connected to said cooling element. 

1. In a method of refrigeration which includes a. expelling refrigerant from absorption solution at a place of vapor expulsion and flowing solution weak in refrigerant therefrom to a place of absorption, b. liquefying the expelled refrigerant at a place of condensation and flowing the condensate to a place of evaporation, c. evaporating the refrigerant in the presence of an inert gas at the place of evaporation to produce a refrigerating effect, d. circulating the inert gas in a circuit between the place of evaporation and the place of absorption, and e. flowing solution rich in refrigerant from the place of absorption to the place of vapor expulsion, f. the place of evaporation being subject to formation of frost due to said refrigerating effect, g. the steps of collecting liquid in a trap above a first level to close and seal the lower end of the trap, h. continuing to collect liquid in the trap above a second higher level to block the circulation of inert gas in the circuit to melt any frost formed at the place of evaporation, and i. continuing to collect liquid in the trap until it reaches a third higher level to remove liquid from the trap and open the seal at the lower end thereof.
 2. The method set forth in claim 1 in which the liquid collected in the trap above the second higher level blocks the circulation of inert gas in that part of the circuit in which inert gas rich in refrigerant flows from the place of evaporation to the place of absorption.
 3. The method set forth in claim 1 in which the liquid collected in the trap above the second higher level blocks the circulation of inert gas in that part of the circuit in which inert gas weak in refrigerant flows from the place of absorption to the place of evaporation.
 4. The method set forth in claim 1 in which the liquid collected in the trap above the first level closes and seals the lower end thereof to initiate the production of refrigeration at the place of evaporation.
 5. Absorption refrigeration apparatus of the inert gas type comprising a. interconnected parts including b. a gas circuit having a cooling element in which liquid refrigerant evaporates in the presence of inert gas to produce a refrigerating effect, c. means for blocking circulation of inert gas in its circuit, said means being arranged to collect liquid above a first level to second and third higher levels, d. said means being rendered operable to block circulation of inert gas in its circuit responsive to the liquid therein reaching the second level, and e. said blocking means embodying provisions for transferring liquid therefrom to another part of the apparatus responsive to the liquid therein reaching the third level.
 6. Absorption refrigeration apparatus as set forth in claim 5 in which a. said means for blocking circulation of inert gas comprises a trap having a pair of upstanding legs arranged to collect the liquid, and b. said inert gas circuit including at least one leg of said trap, c. said trap being rendered operable to block circulation of inert gas in its circuit responsive to the liquid therein reaching the second level.
 7. Absorption refrigeration apparatus as set forth in claim 6 in which said provisions embodied in said blocking means for transferring liquid therefrom to another part of the apparatus comprises a siphon.
 8. Absorption refrigeration apparatus as set forth In claim 7 in which said gas circuit includes an absorber and a vessel connected to receive liquid from said absorber, the outlet of said siphon being connected to discharge liquid to said vessel.
 9. Absorption refrigeration apparatus as set forth in claim 5 in which a. said gas circuit includes an absorber, first conduit means for flowing inert gas weak in refrigerant from said absorber to said cooling element and second conduit means for flowing inert gas rich in refrigerant from said cooling element to said absorber, b. said means for blocking circulation of inert gas being constructed and arranged to block the circulation of inert gas in said first conduit means.
 10. Absorption refrigeration apparatus as set forth in claim 9 in which a. said absorber includes an absorber vessel connected to receive liquid from said absorber, b. said cooling element comprising an elongated hollow member and one section of said first conduit means including piping extending lengthwise within said hollow member, c. another inclined section of said first conduit means being interposed between said one section thereof and said blocking means, and d. a conduit depending downward from the juncture of said one and other inclined sections of said first conduit means, said last-mentioned conduit having a lower open end which is below the liquid surface level in said absorber vessel.
 11. Absorption refrigeration apparatus as set forth in claim 5 in which a. said gas circuit includes said cooling element and an absorber, first conduit means for flowing inert gas weak in refrigerant from said absorber to said cooling element and second conduit means for flowing inert gas rich in refrigerant from said cooling element to said absorber, b. a circuit for circulation of absorption liquid including said absorber and a vapor expulsion unit, c. means including a vapor line and a condenser interconnecting said vapor expulsion unit and said cooling element, d. said means for blocking circulation of inert gas comprising a trap having a pair of upstanding legs, one of said legs forming a part of said first conduit means of said gas circuit and the other of said legs being connected to receive vapor from said vapor expulsion unit, and e. said first conduit means of said gas circuit including piping depending downward in said one leg of said trap and having the lower open end thereof below the level to which liquid can rise in said one leg.
 12. Absorption refrigeration apparatus as set forth in claim 11 in which the other of said legs of said trap connected to receive vapor from said vapor expulsion unit, in an upward direction from a region at substantially the same level as the lower open end of said piping, has a cross-sectional area smaller than that of other parts of said trap.
 13. Absorption refrigeration apparatus as set forth in claim 5 in which a. said gas circuit includes an absorber, first conduit means for flowing inert gas weak in refrigerant from said absorber to said cooling element and second conduit means for flowing inert gas rich in refrigerant from said cooling element to said absorber, b. said means for blocking circulation of inert gas being constructed and arranged to block the circulation of inert gas in said second conduit means.
 14. Absorption refrigeration apparatus as set forth in claim 13 in which a. said absorber includes an absorber vessel connected to receive liquid from said absorber, b. said second conduit means being connected to said absorber vessel, c. said means for blocking circulation of inert gas comprising a trap in said second conduit means, and d. said provisions embodied in said blocking means for transferring liquid therefrom to another part of the apparatus comprising a siphon.
 15. Absorption refrigeration apparatus as set forth in claim 14 in which the discharge end of said siphon is connected to said absorber vessel.
 16. Absorption refrigeration apparatus as Set forth in claim 5 which includes a. a condenser for liquefying refrigerant vapor and a conduit for conducting liquid refrigerant from said condenser to said cooling element, b. said last-mentioned conduit being heat conductively connected to said cooling element. 